The Song:Song Reader is filled out with lots of fragments of songs, and this is one in which only one tiny excerpt was included.
It appears on the back of "Sorry," in a collection of songs about being sorry: "If You're Sorry, Then Why Don't You Look Sorry?," "Are You Really?," "Stop Being A Baby," and "Don't Apologize." Each one has a different pseudonym attached to it, though Beck wrote the short melody/one line of lyrics for each.
"Are You Really?" says it is by Mabel Tanner (as far as I can determine, a made-up name).